UK was warned of July suicide attacks

Senior White House officials have confirmed that Britain received a warning about a potential attack on London involving a cell of four bombers just a few months before the July atrocities in which 52 people were killed.

In the wake of the revelation, bomb victims' families have renewed calls for the government to hold a public inquiry to find out whether vital intelligence was missed that could have prevented the attack.

In August The Observer revealed that Saudi intelligence had passed warnings to British and US intelligence in Riyadh in December 2004 about a terror plot aimed at London.

At the time the Foreign Office refused to comment on the claim, but privately downplayed the suggestion. Yet well-placed sources have now said that senior counter-terrorism officials at President Bush's National Security Council have confirmed that such a warning was received by American and British officials early last year.

The British authorities receive a lot of general information about the terrorist threat, but the details of the plot obtained by the Saudi authorities were specific. British intelligence was told an attack was being planned by four Islamic militants and some of them would be British citizens. The information suggested the attack would take place within six months and target the Underground or a London nightclub. A Saudi security adviser said he was 'convinced' that the information they passed on was 'directly linked' to the July plot.

The revelation will raise serious questions about the decision to lower the threat level to Britain three weeks before the attacks. It is understood that the House of Commons Intelligence and Security Committee, which is investigating various intelligence issues surrounding 7 July, is keen to discover whether the decision was correct.

Parents of victims of the July bombings have been calling for a full public inquiry into the tragic events after mounting evidence has emerged of potential intelligence mistakes, including disclosures that two of the bombers, Mohammed Sidique Khan and Shahzad Tanweer, were known to MI5, the British security service.

Marie Fatayi-Williams, whose son, Anthony, 26, died in the Tavistock Square bus attack, has accused the authorities of treating relatives with disdain in not holding a full inquiry. Responding to claims that the Saudis warned the UK of an attack, she said: 'Whatever lapses happened, we need to know. We need to learn from the mistakes to ensure it does not happen again. We need to know our loved ones did not die in vain. They have not given one good reason why they do not want a public inquiry. What are they trying to hide?'

Saudi authorities claim they obtained the information after a Saudi militant was arrested. The Saudis say that during his interrogation the militant told them he was on a mission to fund a plot to target London. He handed over a Syrian telephone number from which he said he was to be given orders.

He described the main 'disperser' of funds to Islamic extremists in Britain as a Libyan businessman, who is the subject of an international intelligence operation.

A spokeswoman for the Foreign Office said: 'The government takes all reports of alleged or possible terrorist threats or activity extremely seriously, and all reports are thoroughly investigated. But we do not comment on the outcome of such investigations.'